Post on 16-Oct-2020
High temperature gradient micro-sensors for flow separation control
Cecile GHOUILA-HOURIa,b
Romain VIARD c, Quentin GALLAS b, Eric GARNIER b, Alain MERLENa,b, Abdelkrim TALBIa, Philippe PERNOD a
aUniv. Lille, CNRS, Centrale Lille, Univ. Valenciennes, ISEN, UMR 8520 - IEMN, LIA LICS/LEMAC, F-59000 Lille, FrancebONERA, Chemin de la Hunière 91123 Palaiseau, France
cFluiditech, Thurmelec, 68840 Pulversheim, France
Flow separation control
2
• Adverse pressure gradient
• Sharp edges geometry
Flow separation
• Re-attaching a separated flow
• Avoiding / Delayingseparation
Flow separation control
• Real-time adaptation
• Energy saving
Closed loop
Gad-el-Hak
Journal of Aircraft 38 [2001]
Wall shear stress sensors
3
Need for:
• Time-average values: global state of the flow
• Time-resolved values: unsteady structures in the flow
• Direction of the wall shear-stress vector
Several technologies have been developed
• Floating-element sensors
• Optical sensors, micro-fences
• Thermal sensors (hot-film sensors)
J.J. Miau et al.
Sensors and
Actuators A: Physical
[2015]
T. Von Papen et al.
Sensors and
Actuators A: Physical
[2004]
Chandrasekharan et
al.
Journal of MEMS
[2011]
Thermal sensors
4
Hot-films are commonly used in aerodynamics
Calorimetric sensors:
• Another type of thermal sensor
• Use for mass-flow measurement
• Applications for medical domain, home-
appliance,…
Löfdahl and Gad-el-Hak
Meas. Sci. Technol.10 [1999]
Advantages
• Commercially available (Dantec Glue-on-Probe)
• Easy to implement at the wall
• Commercially available electronics
Well known disadvantages
• Insensitive to flow direction
• Substrate effects impact the dynamic response
Kuo et al
Micromachines [2012]
Outline
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
5
Design of the wall shear stress micro-sensors
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
6
Design of the wall shear stress micro-sensors
7
• Calorimetric wall shear stress sensor
• Metallic wires: 1 mm x 3 µm x 730 nm (central)/330 nm (lateral)
• Periodic SiO2 micro-bridges for mechanical support
• Uncoupled heater and measurement wires
• Patent by IEMN LICS/LEMAC
R. Viard, A. Talbi, P. Pernod, A. Merlen, and V. Preobrazhensky, “MiniaturisedSensor Comprising A Heating Element, AndAssociated Production Method,” 2013. FR2977886 (A1) 2013-01-18 WO2013008203 (A2) 2013-01-17 WO2013008203 (A3)2013-03-07 CN103717526 (A) 2014-04-09 EP2731908 (A2)2014-05-21 US2014157887 (A1) 2014-06-12 EP2731908 (B1)2015-09-09 DK2731908 (T3) 2015-12-21.
Micro-fabrication of the sensors
8
4mm30µm
• TCR: 2380 ppm/°C
• Elevation of temperature: 9°C/mW
Electrical and thermal characteristics
Flexible packagingApplied Physics Letters,
DOI 10.1063/1.4972402
[2016]
Calibration in flat plate
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
9
Wind tunnel
Wind tunnel characteristics• 30 cm x 30 cm test section
• Flow velocity up to 40 m/s
Wall shear stress evaluation
• Relation of Coles-Fernholz:
– 𝐶𝑓 = 2 ∙1
𝑘∙ ln 𝑅𝑒𝜃 + 𝐶
−2
– 𝑘 = 0.384
– 𝐶 = 4.127
– 𝑅𝑒𝜃 = Τ(𝜃 ∙ 𝑈∞) 𝜈
• Wall shear stress and skin friction coefficient
– 𝜏 =1
2∙ 𝜌 ∙ 𝑈∞
2 ∙ 𝐶𝑓
• Hot-wire probe measurements from 0.3 mm to 35 mm to provide the velocityprofile in the boundary layer and the experimental momentum thickness ϴ
11
Calibration on a flat plate
2 modes of operation: constant current and constant temperature modes
Calibration curves fitting 4th order polynomial
Sensibility to the flow direction
12
C. Ghouila-Houri et al. Applied Physics Letters, DOI 10.1063/1.4972402 [2016] & Sensors and Actuators A DOI10.1016/j.sna.2017.09.030 [2017]
Flow separation detection on a step-like obstacle
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
13
Flow separation due to sharp edges geometry
Experiment setup
• Obstacles of different heights• 38 mm
• 19 mm
14
Sensor location in the
recirculation region
Flow separation detection
15
MEMS response
Deduced wall
shear stress
variations
C. Ghouila-Houri et al.
Sensors and Actuators A
DOI10.1016/j.sna.2017.09.030
[2017]
Flow separation detection
16
• Obstacle 38 mm x 38 mm
• Varying distance between the sensor and the obstacle
• Upstream flow velocity: 25 m/s
• ReH = 61.103
H 𝑥
Small eddy near
the obstacle
Separation length
Reattachment
Reattached flow
Work in progress…
Preliminary results on active flow control on a flap model
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
17
Integration of the sensors in a flap model
18
12 micro-sensors integrated in the flapmodel
L1 wind tunnel in ONERA Lille (2.40 m of test section diameter)
Miniaturized electronics
Flow control with pulsed jets (Festo MHE2)
Work in progress…
First results of active flow control
19
Sensor near the leading edge
Control by Festo actuators MHE2 (20 g/s;
60 Hz for pulsed mode)
Efficiency to re-attach a separated flow
Separated flow
Attached flow
Thèse T. Charbert, ONERA
Thèse T. Charbert, ONERA
Preliminary results on a pressure thermal micro-sensor
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
20
Preliminary results on a pressure thermal micro-sensor
21
Pressure sensing based on Pirani effect, exploiting the pressure-dependent thermal conductivity of a gas at the molecular range
Dimensions Wires: 1 mm x 3 µm x 730 nm Bridges: 20 µm x 2 µm x 500 nm
Cavity reduced to 170 nm for maximum sensitivity at atmospheric pressure
C. Ghouila-Houri et al
Applied Physics Letters, vol. 111, issue 12 [2017]
Conclusion & Perspectives
I. Design of the wall shear stress micro-sensors
II. Calibration in flat plate
III. Flow separation detection on a step-like obstacle
IV. Preliminary results on active flow control on a flap model
V. Preliminary results on a pressure thermal micro-sensor
VI. Conclusion & Perspectives
22
Conclusion & Perspectives
Wall shear stress MEMS sensor designed for flow control
Fabrication using micro-machining techniques
High temperature gradient for low power
Low-cost mass production
Wind tunnel experiments
Wall shear stress static calibrations in CC and CT modes
Detection of flow separation due to a step-like obstacle
Integration of 12 MEMS sensors in a flap model and 1st results of active flow control
Introduction of a thermal based pressure sensor
Pirani principle
Maximum of sensitivity at atmospheric pressure
Perspectives
Improvement of the CT electronics
Dynamical calibration of the micro-sensors (wall shear stress and pressure)
Integration of a micro-sensor inside a synthetic jet slot
Closed-loop active flow separation control using the micro-sensors
23
Acknowledgments
Thank you for your attention !
Questions ?
24
Partners:
French National Research Agency (ANR) in the frame of the ANR ASTRID “CAMELOTT” project for financial support
ELSAT 2020 – CONTRAERO
RENATECH the French national nanofabrication network